UEFA has threatened to disqualify Russia and England from Euro 2016 if there is any further violence by soccer fans during the tournament in France.
Earlier on June 12, European soccer’s governing body said it had opened disciplinary proceedings against Russia following violence between Russian and English fans in the southern French city of Marseille.
The June 11 violence at the Stade Velodrome venue came after England and Russia tied each other 1-1, with Russian fans rushing at the England supporters in the stadium and breaking through security barriers meant to separate rival supporters.
UEFA said Russia, which is preparing to host the 2018 soccer World Cup, was charged with crowd disturbances, racist behavior, and launching fireworks.
The football authority's control, ethics, and disciplinary body will judge the Russian case on June 14 ahead of its second match with Slovakia on June 15.
No case has been opened against the English Football Association.
But UEFA's executive committee later said "it will not hesitate to impose additional sanctions on the Football Association (FA) and the Russian Football Union (RFS), including the potential disqualification of their respective teams from the tournament, should such violence occur again."
Russian Sports Minister Vitaly Mutko said he agrees with UEFA's decision to launch proceedings against the Russian Football Union (RFU) for crowd disturbances.
"It's the right thing, there were flares, there was a flare gun, there had been clashes in the stands, it's necessary to sort all of this out," the R-Sport news agency cited Mutko as saying.
Mutko criticized the behavior of Russian fans and conceded that UEFA was likely to impose a fine. But he also laid the blame on the match organizers for failing to separate supporters.
The Russian Football Union headed by Mutko expressed "regret over the disturbances” and told fans to "show respect to the opponent and its fans.
Russia's matches are "under the intense scrutiny of international football disciplinary bodies," it warned.
The English Football Association said it was taking the warning "with utmost seriousness."
UEFA held emergency meetings on June 12 to reassess security measures inside 10 stadiums being used across France.
The European soccer authority said there were "segregation issues" at the stadium and that it would strengthen the deployment of security personnel at stadiums.
"UEFA expresses its utter disgust for the violent clashes that occurred in the city center of Marseille, and its serious concern for the incidents at the end of the match inside Stade Velodrome," UEFA said. "This kind of behavior is totally unacceptable and has no place in football."
A decision on the sanctions to be imposed will be made within the next few days, UEFA added.
The UEFA disciplinary panel judges at those proceedings also could take the previous history of violence by Russian fans into consideration, including attacks on stadium security staff at Euro 2012 in Poland.
Meanwhile, French media reported clashes late on June 11 in the southern French city of Nice between fans from Northern Ireland and locals.
That violence also included clashes between fans and riot police.
At least 44 people were injured in clashes in both Marseille and Nice.
Regional police chief Laurent Nunez said four people were seriously injured in Marseille and one of them -- an England supporter -- was in a serious but stable condition. In total, 15 people have been arrested, seven on June 11 and eight more on June 12.
There had been trouble the previous two days in Marseille, which escalated to clashes in another part of the city between soccer fans from Russia, England, and France on June 11 before the match.
Also on June 12, French Interior Minister Bernard Cazeneuve said alcohol restrictions near "sensitive" venues would be extended, with sales bans on match days and the eve of match days.
With reporting by AP, Reuters, BBC, AFP, TASS, and Interfax